Step 1: Master the basic concepts and formulas
1) Basic parameters of the cylinder
Cylinder diameter D (cylinder inner diameter), rod diameter d (piston rod diameter), stroke S, use pressure P, installation method, and installation size.
One of the most important is the cylinder diameter, stroke. The use of pressure cylinder diameter has a standard series of options, and the use of pressure is also divided into several files
2) F = PS
From the formula of force calculation, we can see: F = PS (P: pressure; S: Compression area - determined by cylinder diameter and rod diameter of the cylinder)
For example, the thrust of the cylinder needs to reach 10 tons; that is, F=10, then P and S have a variety of combinations.
100 cylinder diameter cylinder, the use of pressure to 14MPA can reach 10 tons
80 cylinder 80-cylinder-diameter cylinder, the use of pressure to 21MPA can also reach 10 tons
Step 2: Determine the system pressure P
1. Primary hydraulic working pressure:
The choice of pressure depends on the size of the load (i.e., F) and the type of equipment. Also consider the limitations of assembly space, economic conditions, and component availability of the actuator.
In general, for equipment with a fixed size that is not too limited, the pressure can be selected lower, and the walking machinery should be selected higher.
Step 3: Select cylinder diameter D/ rod diameter d
After the design pressure is selected, that is, P is known, and the load size F is known, then the force area of S is obtained by the formula, and the bore of the cylinder is calculated according to the force area
Step 4: Select trip S
According to the requirements of the overall design of the equipment or device system, determine the installation mode and stroke S The specific determination principles are as follows:
Travel S actual maximum working travel Smax travel quantity △S;
Trip allowance △S, trip allowance △S1+, trip allowance △S2+, trip allowance △S3.
Step 5: Installation mode, that is, in what form the cylinder is connected to the equipment. After determining the installation method, determine the installation size.
Determine the installation mode
1) Flange installation
2) Hinge installation
a) Tail single (double) earring installation
b) Mounting of end, middle, or tail trunnons
c) The installation condition of the tail trunnion is similar to that of the tail pair earrings, and the selection method is the same as above.
3) Tripod installation
How to select hydraulic cylinder
How to select hydraulic cylinder
How to select hydraulic cylinder
How to select hydraulic cylinder
Step six: Selection of end buffer
The following conditions should be considered to choose two-end buffer or one-end buffer:
1) The hydraulic cylinder piston is running in full stroke, and its round-trip running speed is greater than 100mm/s; both ends of the buffer should be selected.
2) When the single yearning (return) speed of the hydraulic cylinder piston is greater than 100mm/s and it runs to the end of the stroke, one or both ends of the buffer should be selected.
3) Other specific conditions.
Step 7: Oil port type and diameter selection
1) Oil port type:
The selection of the internal thread type, flange type, and other special types is determined by the nozzle mode of the connecting pipe in the system.
2) Oil port diameter selection principle:
Under the condition that the medium flow rate in the connection pipeline between the system and the hydraulic cylinder is known, the medium flow rate through the oil port is generally not more than 5mm/s, and pay attention to the factor of speed ratio to determine the diameter of the oil port.
How to select a hydraulic cylinder
Step 8: Select the conditions under specific working conditions
1) Working medium
Normal medium for mineral oil, other media must pay attention to its impact on the sealing system, the material characteristics of each component, and other conditions.
2) Ambient or medium temperature
The normal working medium temperature is -20℃ to +80℃; beyond the working temperature must pay attention to its impact on the sealing system, the material characteristics of each component, the cooling system Settings, and other conditions.
3) High running accuracy
For servo or other hydraulic cylinders with low starting pressure requirements above medium and high pressure, it is necessary to pay attention to their impact on the sealing system, the material characteristics of each component, and the details of the design.
4) Zero leakage
For hydraulic cylinders with specific pressure retention requirements, it is necessary to pay attention to their impact on the sealing system, material characteristics of each component, and other conditions.
5) Working pressure, speed, working conditions such as
a) Medium and low pressure system, piston round-trip speed ≥70~80mm/s
b) Medium and high pressure, high pressure system, piston round-trip speed ≥100~120mm/s
It is necessary to pay attention to the impact on the sealing system, the material characteristics of each component, the connection structure and the matching accuracy.
6) High-frequency vibration working environment: must pay attention to its impact on the material characteristics of each component, connection structure, and detailed design, and other factors.
7) Low temperature icing or a polluted working environment, such as
a, high dust and other environmental;
b, water, acid mist or salt mist, and other environments.
Attention must be paid to its impact on the sealing system, the material characteristics of each component, the surface treatment of the piston rod, and the protection of the product.
Step 9: Selection of seal quality
Condition 1, no specific conditions, specific quality requirements, according to the standard sealing system,
Situation 2, as previously mentioned in the specific working conditions, no specified quality requirements, according to the specific sealing system;
Situation 3, as previously mentioned in the specific working conditions, there are specified quality requirements; it is recommended that the sealing system be recommended by professional engineers;
Situation 4, the hydraulic cylinder sealing system failure consequences are serious (such as affecting safety, not easy to replace, large economic losses, etc.), it is recommended that the sealing system be recommended by the industry engineer;
Situation 5. For the hydraulic cylinder sealing system supporting export, it is recommended that professional engineers recommend well-known sealing quality with good interchangeability and easy procurement according to working conditions.
Step 10: Selection of other features
Exhaust valve
According to the working position of the hydraulic cylinder, it is normally set at the highest point of the final deposition of air at the end of the two chambers, which can prevent crawling and protect the seal after the air is exhausted, and can slow down the deterioration of the oil.
In the working environment where the oil leakage is strictly prohibited, due to the long stroke of the hydraulic cylinder or some working conditions, the oil accumulates behind the dust ring during its round-trip work to prevent leakage after a long time of work, and the leakage port must be set in the position where the oil accumulates.
